The goal of this research is to evaluate the role of infection in the pathogenesis of chronic bronchitis and emphysema. A study population of 67 adults who have these diseases of varying severity, and 20 normal control subjects, will be closely monitored over a period of seven years for episodes of acute respiratory illness and for changes in pulmonary function. Appropriate cultures for pathogenic bacteria, fungi, viruses and mycoplasma will be taken both during and between periods of acute illness. Infections with these agents will also be diagnosed by serologic and immunologic methods. Clinical, physiologic and microbiologic data will be correlated by computer analysis for evidence that specific infectious agents are related to the onset or progression of this disease. If specific agents are found to be of pathogenic significance, the use of preventive and therapeutic procedures will be evaluated. The role of smoking, air pollution and genetic factors will also be assessed so that role of infection can be placed in perspective.